


go fuck yourself

by Spectascopes



Category: Undertale (Video Game)
Genre: M/M, Plot What Plot/Porn Without Plot, Porn, Sanster, Unexpected Sex, magic fleshlight, no family relationship, science colleagues sans n gaster
Language: English
Status: Completed
Published: 2016-02-03
Updated: 2016-08-04
Packaged: 2018-05-17 22:57:59
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 4
Words: 10,667
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5888497
Author URL: https://archiveofourown.org/users/Spectascopes/pseuds/Spectascopes
Summary: <blockquote class="userstuff">
              <p>In which a chronically late and immature scientist thinks it'd be hilarious to 'prank' his boss by using his sex toys without permission.<br/>Results: Gaster breaks his favorite coffee mug and Sans is going to pay for it.</p>
            </blockquote>





	1. Chapter 1

**Author's Note:**

> Me n my pals were discussing the magic flesh light phenomenon and so this train wreck was born  
> read at your own risk. it's obviously nsfw

 

“heh i bet you've got a massive _blaster_ , gaster.”

“oh man g you gotta stop bending over like that you're giving me a _bone_ -r.”

“hey doc when you're in bed but you're going too slow do they say “please go a little w. d. _faster_.”

 

It was like a competition for Sans, and Dr. Gaster was well aware of that. He was one of the brightest scientists of his age, yet he was also quite possibly the most inappropriate and childish monster to be born in centuries. He wanted to see what would get a rise out of his senior colleague, and when the puns stopped sufficing he'd turned to less innocent means.

Sans was working on a converter for the Core, running calculations and figuring out the best way to go about crafting such a thing. Gaster watched him from where he worked on some conversions for the cooling system that would be installed in the finished energy plant. When he wasn't being an ass, Dr. Sans had a commendable work ethic and an IQ higher than even the Royal Scientist's

“Sans, I'll be running some queries tonight and will be staying in the lab. I need you to stop at my home on your way here tomorrow and pick up the energy conversion formulas I've been working on. I didn't anticipate needing them for another couple of days yet, but we're ahead of schedule.”

“sure thing, boss,” Sans replied. He didn't even look up from his work.

“Dr. Sans.”

“i heard ya, boss, stop at your house and get your formulas. And i told ya not to call me doctor unless the king's here.”

“It's half past ten, Sans.”

The scientist jumped and looked up at the clock, bringing a smirk to Gaster's face.

“shit, i'm gonna be late, papyrus is gonna kill me,” Sans worried as he threw the things he'd been using together onto the desk and hurried over hang up his lab coat. “why didn't you tell me sooner, g?”

“I did. Half an hour ago. Aren't you forgetting something?”

Sans was halfway out of the lab when Gaster spoke. He stopped and looked at his superior for a moment.

“uh, no?”

“And you're going to get into my house how, exactly?” Gaster asked.

Sans groaned and slapped his face, hustling over to the doctor's desk and waiting for him to dig his keys from his pockets. He bounced on his feet.

“take your time sir, please,” he said harshly. “papyrus is gonna be home any minute and if i'm not back when he gets back he'll call half the underground trying to find me.”

“Your being late occurs so often that I can hardly imagine he'd assume you were anywhere but here.”

“it's pap, don't be logical,” Sans scolded, but he was grinning. “can't believe i'm gonna see the great dr. gaster's house, though.”

Gaster shook his head. “The files are on the desk in my bedroom.”

Sans snatched the keys from his hand as soon as he had it up and practically ran to the door.

“catch ya later, hot stuff!” Sans shouted. Gaster felt a blush rise to his cheeks.

“Sans!” he scolded even as he inwardly cursed the heat. Sans lingered just long enough to see the fruits of his labor, flash the Royal Scientist a shit-eating grin, and then leave without another word.

 

Sans did exactly as he was told the following morning. He left, promptly half an hour late, breakfast 'dog shoved into his mouth and Papyrus shouting after him to “get to work on time for once you lazy bag of bones!”

He would've forgotten about the errand entirely if he hadn't reached into his coat pocket and felt the jingle of unfamiliar keys inside. Gaster's house was near the capital, Sans had escorted him home a few nights when they'd worked late and the short skeleton wanted to see the usually-composed man at a loss of what to do. It was hilarious to watch him grumble and complain about something as simple as walking home with a colleague. It was so easy to do.

Sans didn't hesitate to admit to himself that he'd get funky with the Royal Scientist any day. He liked to believe Gaster felt the same, based on his reactions to Sans's blatant flirting, but the man was aloof. Dr. W. D. Gaster was a mystery to Sans- and that just made the tall, slender skeleton all the more desirable.

Sans's thoughts of getting take-out for dinner came to an end when the unfamiliar house came into view. He quickened his pace, well aware that he was going to be at least an hour late for work, but not really finding it in himself to care. It wasn't like he didn't put in his time. He and G. worked late nearly every night, long after the other employees and volunteers and interns had gone home.

He unlocked the door and stepped inside, preparing himself for some weird, unfurnished home, or a mini lab inside of the doctor's house. As he closed the door behind him, he was surprised to find that the home looked... strangely normal. It wasn't very large, given that only Gaster lived there as far as Sans knew, and it was simple yet elegantly styled. Gaster sure did like his geometric shit. Sans grinned at the small living area, neat and orderly like all of his boss's things were, and imagined Gaster sitting there doing... whatever it was the man actually did outside of work. Did he even _do_ anything else? Sans questioned if Gaster knew what “leisure time” meant.

“honey, i'm home,” Sans announced as he took off his dirty sneakers and headed into the one-story home. He flicked a few of the lights on but found nothing too scandalous. To his utter dismay, Gaster had actually left a few dirty dishes carefully stacked beside his sink.

“oh man, dings, this is disgusting,” Sans said to himself. Aside from the dishes, the room was pristine. Sans wondered how often the utilities could possibly be used, given that Gaster spent nearly all of his waking hours in the lab. It wasn't like his own kitchen, homely and messy from Pap's lawless excuse for cooking.

Sans inspected each room, finding nothing particularly exciting, until he finally found Gaster's bedroom and office. The room was tucked into the back, the same kind of neat and organized as the rest of the house, but with a little more personal touch added. The walls were painted a nice cream color, with a queen sized bed and geometric-patterned area rug. Gaster's desk was quite simple and humble. Sans smirked as he walked over and jumped on the bed, flopping on his stomach and making sure to disturb the nicely made covers. Who in the hell actually made their bed every morning? Well, Papyrus did, too, but that was Papyrus. He was neat and clean like Gaster was. Sans was surrounded by freaks.

If it had been anybody else's home, he would've kept to the task at hand, grabbed the file he knew he'd find right where Gaster'd said it would be, and leave without another word. But this was _Dr. Gaster's_ house, and Sans was... Sans.

Each drawer contained it's own little secrets. The closet was bland, filled with dark colored clothing and shoes and loads of boring Hot Shot Royal Scientist clothing. Sans opened up a dresser drawer and discovered underwear.

“oh dings, i'm swooning,” he joked, holding up a neatly folded pair of boxers. He heard something move around in the bottom of the drawer and stopped for a moment.

“oh boy... what secrets are you hiding, g... what've you got in your-” Sans reached in and pulled out the object, only to drop it like it was on fire half a second later.

A flesh light.

“holy shit!” Sans barked, laughter bubbling in his chest. The toy rolled to a stop on the floor where Sans had dropped it, but he was too busy carrying on to even look at it.

“i can't believe this- no way. i'm dreaming. he has a _flesh light?_ holy fucking hell, dings, oh my god,” Sans nearly cried, stepping back and falling on the bed to laugh. “this is better than anything i could have ever hoped for. oh my god. a _flesh light_ oh my god-”

Sans stopped. An idea had just blossomed in his mind, intrusive and gross. But then he sat up and looked at the 'innocent' black sex toy on the carpet and folded his hands thoughtfully in his lap.

He battled with himself for a moment. He wanted to laugh again, but he was also staring down at the scandalous object on the ground below him. It was rather simple (Did the doctor's love of that style extend even to his sexy times?) and lacked any sort of intimate detail. It clearly wasn't a replica of other, more mammalian monster's nasty bits. From Sans's own personal experience, it was modeled after the magic entrances skeletons were able to conjure on their own pelvis's with a little bit of magic flare. Sans smirked at the thought.

“gaster... you dirty skeleton...” Sans murmured smugly. This turn of events was incredible, but he could only deny that he was turned on as all fuck for a little while. He thought of Gaster- the aloof, composed, stately Dr. Gaster- jerking off with his flesh light, thrusting into the toy and moaning with that lovely purple blush across his face-

Sans stopped his mental train, but he'd long come to terms with the fact that W. D. Gaster was hot as hell. He smiled and reached down to pick up the intimate object, turning it over and inspecting it carefully. It was a strange consistency, slightly purple- tinged and translucent, with... a bit of glitter, maybe? The thought made Sans snort. Would the scientist really order a custom-made flesh light? The thought was tantalizing. Sans ignored the growing warmth in his pelvis and brought a finger up to his mouth.

He formed a tongue with practiced ease and stuck the finger in his mouth, making sure to get it nice and wet before he took it out again. He hesitated for only a moment before he stuck it inside of the toy, pleasantly surprised to find the material slightly warm to the touch. Knowing Gaster, he would keep the thing clean as hell.

Sans grinned to himself. He was going to use Gaster's flesh light.

 

 

Gaster sat in his personal office, tapping his pen impatiently against the desk. Sans was already half an hour late. He needed those papers before he could continue his work, and he didn't want to begin something else entirely while there was still so much work to be done. He'd expected as much from his co-worker, however. It was extremely rare that Sans came to work on time unless his brother accompanied him. Papyrus might be loud and disturbingly cheery, but he was prompt, tidy, and absolutely nothing like his elder brother. Gaster could appreciate that.

He picked up his favorite mug, a simple black cup with a matte finish, and took a sip of coffee. Dr. Fontaine was quite literally a genius, and could he ever live up to his full potential Gaster would be without a job. It had taken the scientist years to realize that, unlike himself, Sans put other things before his work. It had frustrated him for the longest time, because Sans could be doing such incredible work, and he knew that, too. But he was a clown, and his first priority was and would always be his little brother.

Still, Gaster had risen at eight and Sans was to be there at nine thirty sharp. It was nearing eleven and there was still no sign of the short-statured skeleton.

Gaster lifted the cup to take another swig of coffee when he felt something... off. He paused for a moment, unsure of the feeling. He shifted in his chair. It felt as though ghostly fingers were touching him, gentle enough that he could barely feel it, but certainly there.

Quite suddenly he felt a finger being thrusted into an opening he didn't actually have and the coffee mug smashed to the ground in a scattering of black, wet pieces of porcelain.

“Hnng-” Gaster moaned, but he put his hands over his mouth to stifle the noise. His body tensed up at the feeling of being explored with a rather eager digit. He heard footsteps coming to the office door. Gaster had only seconds to compose himself before there was a gentle knock and Dr. Alphys popped her head into the room.

“S-sir! Is e-everything okay-”

“Yes thank you Alphys,” he said quickly. He ignored the hot coffee on his pants and the wet finger probing his imaginary entrance. He felt heat come to his cheeks.

The intern pursued her lips and looked around, confused. “U-uhm, are you-”

“Yes quite I'm very sure,” he said quickly. Alphys's eyes went wide as he jerked in his seat a little, but she promptly closed the door and he could hear the pitter-patter of her feet as she walked away.

Sans had entered a second finger. He was not going easy on Gaster's magic sex toy.

“Sans you idiot-” Gaster hissed, but the fingers curled inside of him and he had to bite down on the sleeve of his jacket to keep from letting out another embarrassing noise. He could do little more than hunch his back and brace himself on his desk as Sans pleasured his toy, no doubt assuming that he was just playing some harmless prank on the senior scientist.

Of course Sans would do this. Even as Gaster was wracked with waves of pleasure felt through nothing more than a magical connection, he was well aware that this is exactly what he should have expected from the skeleton. He just prayed that nobody else entered the room.

The fingers explored for a while, feeling the inside of the opening and leaving, only to be re-entered again with more lubricant. Gaster could only assume said liquid was Sans's saliva.

“Sans, I'm going to kill you for this, you-” once more Gaster's embarrassed whisper was cut off as Sans withdrew from the toy for a moment. Gaster let out a deep breath, shaking all over. He felt the heat pooling in his pelvis. The break was very welcome, as the man had only ever had himself to set the pace, and-

His thoughts were cut off as the feeling of a tongue being pushed into his ghostly opening caught him by surprise and a whining moan escaped his lips.

“Hnn- agh, Sans!” he hissed, cursing himself for enjoying it as much as he was. He returned to his position of hunching in his chair, well aware that he was already close and it had only been a couple of minutes.

The feeling of a tongue lapping at him made Gaster shudder and pant and, although it made him feel shameful and particularly lewd, thrust unsuccessfully into the movement. He had absolutely no control over the toy- it was meant to mimic the nerve ends of a conjured opening, not actually _be_ one. Sans could have his way with it and remain completely unaware that Gaster was connected on the other end. The thought made Gaster clench his teeth, but it only made each lick all the more pleasurable.

When Sans finally put the opening to what Gaster could only assume was his own conjured member, the Royal Scientist quite literally shivered in anticipation. He wouldn't lie- he was enjoying this. Sure, he would definitely never let Sans hear the end of this when he got back to the lab, but there was nothing he could do. That thought made the warm pleasure in his pelvis well up, and as he felt himself being penetrated by Sans's cock he bucked his hips forward.

“Faster, Sans, you-” Gaster said through his clenched teeth, but then Sans pulled back and gave a hard thrust.

“Ahh, mm.” Gaster bit down on his sleeve to stifle the moans escaping him, but didn't do anything more to try and stop them. He was beyond that- he knew he wouldn't make it much longer. He let himself rock with Sans's rhythm, getting fucked by him until he was so close he felt ready to burst. His hips and spine burned with magic, hot and warm and so very _good._

“Sans-” he gasped as it all became too much and he shut his jaw and tensed. The climax washed over him, Sans working hard on the other end, his thrusts growing erratic and un-timed. Gaster's magic sparked in the air as he came.

Sans fucked him through the orgasm and then some, and the scientist could only sit and let himself be used as a toy until he felt the warm release of magic and one last painfully hard thrust on Sans's end. He was panting and gasping. Gaster sat back in his chair and closed his eyes, trying to get enough breath into him but also trying to come to terms with the fact that he'd just been screwed senseless by his lazy colleague who probably had no idea what he'd just done.

Sans didn't touch the toy after that. Gaster was extremely glad for that, because he didn't know if he could handle another round.

It took Gaster a while to recover. When he did, he remembered that there was coffee all over the floor, and that his favorite mug was shattered. Sans was going to buy him a new one and he didn't care how much that would cost. He bent down and began to pick up the slick pieces of the mug.

Sans didn't know what had happened. Gaster, for once, had the upper hand.

 

Sans finished into the toy, panting, biting his lip to keep from smiling. He'd imagined Gaster under him the entire time, his slender, handsome frame bare and starkly white compared to the usual dark clothes he wore. Sans dismissed his pseudo-cock with a wave of magic and set the flesh light on the bed beside him. He let out a big puff of air before he grinned lazily up at the ceiling.

He'd just used his boss's glittery purple skeleton sex toy, and god damn had it felt great. Sans was going to tell Gaster what he'd done and he could just imagine the horrified look on the skeleton's face, that perfect shade of violet flushing his cheeks.

Sans picked himself up, pulled his pants back to their rightful position, and grabbed the files from Gaster's desk. The wonderful thing about being a skeleton was that anything sexual was completely magic in nature- no mess, no clean up, just the warm reverberation of the orgasm running through his bones and gathering in his chest to make his steps all the lighter. He was beaming to himself, proud of his day's work.

 

Sans got to the lab about half an hour after he'd finished fucking himself with the Royal Scientist's flesh light. He brushed past the few people he saw on his way in, snatching his lab coat from where he'd placed it the night before, and hurried to Gaster's office. He absolutely couldn't wait to see the man's face- he was giddy with anticipation.

With a few sharp knocks out of the way, Sans pushed open the heavy door to Gaster's personal office and found the monster sitting there, hands folded, chin resting on them.

“hey g, wow, you aren't working? that's not natural. you're always working,” Sans said with a knowing smile. Gaster just stared at him with his mouth hidden by his hands. Sans's grin faltered for a moment.

“uh, doc? what's with that look?”

“I know what you did, Dr. Fontaine,” Gaster said.

Sans opened his mouth to ask him what he meant, but then the glaringly obvious answer came to him and he was quick to shut his jaw and watch Gaster for any sign that he was joking. Sans felt a pit growing in his stomach.

“you... uh, know what?” he ventured.

Gaster didn't move at all, or change his expression. After a moment he let his hands fall to his desk and gave Sans a disappointed frown.

“I know you went to my home and used my personal belonging to pleasure yourself,” Gaster said so matter-of-factly.

Sans's stomach dropped. He looked for any sign of how the _fuck_ Gaster could've known that, but the doctor was already standing up from his desk to reach his full height, nearly twice that of the tiny skeleton.

“u-uh... how... do you know that...” Sans said despite struggling with each word. Was it getting really hot in there or was it just him? Gaster stared him down with a face completely devoid of any sort of humor.

“I designed and created that tool via magic. It replicates my own nerve endings and is a receptacle for sexual pleasure that transmits those feelings to it's creator.”

Sans blinked for a second before the meaning of the words hit him. His eyes went wider than dinner plates and he swore his non-existent stomach dropped to the floor.

“u-u-uh... u-uhm...” he stammered. Gaster's eyes burned into him. He felt sweat drip down his skull.

“I know what you did, Sans,” Gaster repeated. The words fell dark and heavy from his mouth.

Sans stood in shock for a few moments. He'd... he'd actually just... he....

“oh my god. fuck- fuck, g, i'm sorry, holy fucking sh- i'm so sorry g i didn't even realize-” Sans babbled, unable to meet his boss's eyes. He was shaking. Gaster took a few steps towards him and stood over the smaller skeleton like a tree would an ant. “shit. shit, gaster, i'm so fucking sorry, i didn't... oh my god-”

“I expect you to get your month's load done in the next two weeks. Do try to be on time from now on, Dr. Fontaine. You're welcome to stay overnight if the need should arise.”

“y-y-yes sir, of course, sir, i'm... oh my god, i'm so sorry gaster, i... i...”

Gaster moved past him to the door. Sans stood frozen in his place, an overpowering sense of shame and guilt building in him. He felt like he was going to throw up and cry.

“Sans?” Gaster asked. The shorter scientist hung his head and made himself smaller.

“Yes, sir?” he mumbled without turning to look at the Royal Scientist. He wasn't quite sure if he could.

“Please try to inform me next time you decide to engage in sexual intercourse with me.”

Sans clutched his lab coat. “I-I... y-yes, sir, sorry, dr. gaster...”

Sans heard a deep chuckle bubble up from the monster behind him. He whirled around to see the tall man looking down at him with a faint smile on his face.

“Aside from being unexpected, it was quite a pleasant experience. Perhaps we can do it again sometime?” Gaster asked, but before Sans could gather his wits the doctor had swept himself from the room.

Sans stared at the door for another minute and a half before a vibrant blue colored his face and he fell backwards onto his ass.

 


	2. Chapter 2

**Notes for the Chapter:**

> i promised like two people i'd do this, bet you thought you'd seen the last of the classic fanfic "go fuck yourself" lol  
> anyways it'll probably be another, like, two chapters like this and then another (consentual) sexy/smutty finale, so stay tuned for that i guess lol

    Sans was avoiding him. Dr. Gaster was smart enough to realize that almost immediately after their little incident. Whenever he’d enter a room, he’d see the tail end of Sans’s lab coat disappearing around a corner. When he tried to engage in conversation, as direct and straightforward as he could be, Sans replied with as few words as possible, and his eyes would remain glued on the floor.

    As much as he hated to admit it, Gaster had made a mistake. It had seemed obvious at the time to take his upper hand and use it to get Sans back for all the times he’d caused a blush to spread across the doctor’s face, but he’d been very wrong. He felt like an idiot, truly, because it made sense for Sans to be so upset. If the circumstances had been only slightly different, what had transpired could have easily been defined as rape. Not knowingly, of course, but still with the same psychological effects. Gaster had felt that it was obviously not the case, but, as he’d admitted prior, he had been wrong. Sans was under the assumption that he’d unintentionally sexually assaulted Gaster, and it made Gaster’s stomach twist with the realization.

    Gaster sat in his office, knowing full well that his work was subpar because of his worrying. Sans had gone home without so much as a word to his boss.

    Somebody knocked at his door, long past the time that people usually knocked at his door, and his mind immediately went to Sans.

    “Come in,” he called.

    It was indeed another skeleton who poked his head inside, but not at all the skeleton that Gaster was expecting.

    “Hello, sir, I’m sorry to interrupt you at this time of night…” Sans’s younger brother said. He stepped inside, tall and lanky and well-dressed, and shut the door behind him.

    “Papyrus,” Gaster said lamely.

    “Yes, sir, I hope I’m not being too much of a bother-”

    “Nonsense, please, come sit down,” he said immediately. Papyrus was so very different from Sans, with his wide shoulders and thin frame and defined face. He came over, if a little hesitantly, and took a seat in the chair in front of Gaster’s desk. He hardly ever came to the lab, Alphys must have let him in. The monster folded his hands in his lap and waited for his senior to speak.

    “What can I do for you?” Gaster asked. If he recalled, Papyrus had turned 21 a few months prior and was employed as a sentry in Snowdin.

    “If it isn’t too much to ask, sir, I… would like to know if anything has happened. Sans has been… strange this past week, and he refuses to talk to me about it.”

    Gaster sucked in a breath. Ah. So it wasn’t just at work.

    “I know this isn’t conventional, but he speaks so fondly of you… I hope it isn’t rude of me to assume that you might know what’s bothering him, sir,” Papyrus said. He shifted in his seat and smoothed his pristine button-down shirt.

    “It isn’t rude in the least,” he assured the nervous skeleton. “But I’m afraid that what transpired was not… well… appropriate.”

    Papyrus’s eyes went wide, and before Gaster could continue, his boney hands came up to his mouth.

    “It was his puns, wasn’t it? I’m so sorry, sir, I know they can become increasingly lewd, but he doesn’t mean anything by them-”

    “No, no, it isn’t that,” Gaster said, amused by how well Papyrus knew his brother. “He’s been behaving that way since I hired him two years ago. If anything, I find it quite endearing.”

    “Oh…” Papyrus squirmed in his seat for a moment. The few times that he’d interacted with the younger monster, Gaster had always taken him to be quite confident and straightforward. He clutched at his red scarf and cast a worried look to the doctor.

    “Last week,” Gaster began, “I sent him to my home to pick something up for me. He crossed a line, and while I wasn’t upset, I pretended to be in order to play a trick on him. I’m afraid I took it too far, and he believes that things are more tense than they truly are. I’m very sorry, Mr. Fontaine.”

    “Don’t apologize, sir!” Papyrus said immediately. He stood up and waved his arms, a very Papyrus-type action. “Sans is reckless and irresponsible, and if he was the one who stepped out of line in the first place then it’s hardly your fault. And, if he’s acting like he always does, I’m sure he’s avoiding you. He skitters around his problems like a frightened rabbit!”

    Gaster couldn’t help but smile at the comparison. Papyrus seemed to realize that he’d stood up in his passion, and sat back down with a blush across his cheekbones.

    “Sorry, sir, I-”

    “Please, Gaster is fine,” he interjected, and Papyrus gave a hasty nod.

    “Right, sorry, s- I mean, Dr. Gaster,” Papyrus righted himself. “I’m just… I’m very worried. He hasn’t been eating as much, and he’s been sleeping more than usual. It’s been a long time since he’s gotten this low, and I know it’s because he’s refusing to face his worries, but… he’s my brother, sir,” Papyrus said before he sighed and looked away. “I’m sorry.”

    “I understand, Mr. Fontaine-”

    “Oh, please don’t call me that, nobody ever calls me that,” Papyrus said as he rubbed the back of his neck. “Papyrus is fine, sir.”

    “Gaster,” he reminded him with a gentle smile.

    He looked at the monster with confusion in his sockets, but when he saw Gaster smile he returned the gesture.

    “Gaster, yes, my bad,” he said. His nerves seemed to ebb, but he still looked very concerned.

    “Why don’t you tell him to come and see me tomorrow?” Gaster suggested. “If it wouldn’t upset him, let him know you came to see me, and that everything is quite alright. He’s been avoiding me at work, so I haven’t had the chance to talk to him.”

    Papyrus nodded. “Of course, that sounds wonderful.”

    “I feel almost bad, though,” the scientist began. “He’s been getting so much work done this week… but, I’m not sure that is worth the absence of his intolerable puns. I’d much rather have him comfortable than efficient.”

    Papyrus smiled, this time earnestly. He sat up straight in his seat, even taller than Gaster.

    “I yell at him at least four times a week. He’s chronically late, and he sleeps in almost every day, and I know he’s napped at work before! I hope you scold him, too, doctor.”

    “He gets his work done, and that’s all that matters to me in that regard. He’s extremely intelligent.”

    “He never applies himself…” Papyrus huffed.

    “Oh, that isn’t true,” Gaster said. “He seems to apply himself fully in his duty as a brother.”

    Papyrus laughed. It was a wonderful noise. Gaster understood why Sans loved his brother so much.

    “That’s very true. As great as I am, I must admit, he is even greater. And not just intellectually! Did you know he can cook? And while his cleaning skills are not the best, he has excellent hand-eye coordination, we play table tennis sometimes and he-”

    Papyrus went on about how incredible his older brother was, and Gaster couldn’t help the warm smile that broke out on his face.

   

   

   


	3. Chapter 3

**Notes for the Chapter:**

> next chapter is gonna be the last one, i think y'all know what's gonna happen after that dinner B)
> 
> if there's mistakes lol forgive me i edited this while drunk  
> (as always follow me on tumblr @theperfecta for softcore memes, you can even buy me a coffee if you wanna be a real cool cat, i mean honestly i probably will spend it on coffee, i love iced mochas?? like so much. ugh)

Gaster took a big sip of coffee. Sans had checked in, he knew it, but had yet to come and see him. His fingers tapped on his desk with nerves. He couldn’t work like this. He had tried to deny it, but he was very worried about his coworker, and no amount of caffeine was going to fix that.

Papyrus had said that Sans was low. Gaster was a smart man, he knew that not sleeping and refusing food could very well be signs of something much more serious. He always noticed the days that Sans came in with tired eyes and slow jokes, not quite as relaxed as he usually was. Gaster wouldn’t pry, no, he certainly understood what it was like to be faced with illnesses that were beyond physical. In his youth he’d suffered greatly from anxiety, failing classes in school multiple times before he’d come forward and admitted that he simply couldn’t handle it. 

No, he wouldn’t press Sans to talk about his problems, because they really weren’t the issue. But Sans  _ did _ need to talk about the current problem at hand, and that was what had transpired with the now-infamous sex toy.

When noon came and Sans was still a no-show, Gaster took matters into his own hands. He knew Sans ate his lunch in his office, and he knew it took Sans quite a while to “properly enjoy” his food. He stood and made his way to the main area of the lab, where he found Alphys working diligently. 

“Hello, Alphys-”

“Oh my god!” she squeaked as she whipped around and knocked various bolts and nuts on the floor. She craned her neck to look up at Gaster and sucked in a breath.

“O-Oh! Sir, oh, sorry, you scared me!” she stuttered, but she was already down and picking up her spilled metals, tail sticking up in the air. “You’ve been in y-your office all day, I-I figured you were busy.”

Alphys was shorter than Sans, so she was much closer to the ground, but Gaster knelt down and helped her pick up the materials anyways. She was blushing, her yellow scales a warm pink, her glasses slightly askew.

“It’s quite alright,” Gaster said, using his magic to pull some of the more adventitious bolts over to his hands. Alphys stood back up and dusted off her lab coat with her claws before fixing her glasses and giving him a nervous smile.

“O-Okay! Sorry about that, thanks for the h-help.”

“It was my fault they were on the floor in the first place,” Gaster said with a small smile that Alphys returned in full. She set her things back and fixed their positions on the work table before she turned to her boss expectantly.

“S-so, what did you need?”

“Do you know if Sans is eating at the moment?”

Alphys frowned. “Uhmmm… I think so! He said he was going to his office.” Her frown deepened. “Is he a-alright? He’s seemed… o-off.”

Gaster sighed. “That is why I’m on my way to check on him,” he said. Even his other employees were aware that Sans was unwell.

Alphys nodded. “Okay! Well I’m p-pretty sure he’s eating, tell me i-if he’s okay!” 

“I will, thank you,” he said, giving Alphys a quick little pat on the shoulder as another apology for scaring her.

He had a rabbit to corner.

Sans was in his office. Gaster peaked into the open door and saw him staring dejectedly down into what appeared to be a sandwich, which sat next to a brown paper bag that had “HAVE A GOOD DAY AT WORK!” written on it in red marker. 

Gaster pulled away for a moment and steeled his nerves. He’d made a mistake, and he had to fix it. Admitting he was wrong was never his strong point, but he’d do it. He took a deep breath and gave a quick knock on the door.

“come in,” Sans called.

Gaster pushed open the door and Sans jumped out of his chair. 

“o-oh, sir, i was just-”

“Eating lunch?” Gaster asked, trying to keep the mood light. 

“yeah, uhm, sorry, i’ll get back to work-”

“Sans,” Gaster reprimanded, and it made the smaller skeleton flinch. He eyed the door like a cornered animal, and Gaster’s soul twisted with guilt for making Sans feel this way.

“sorry sir,” Sans mumbled, but he kept his eyes on his desk.

“Sans,” Gaster repeated, and perhaps it was his tone, but Sans looked up at him. Gaster’s soul tightened and he began to panic- the monster looked on the verge of tears. He held up his hands.

“I’m sorry, I didn’t mean to upset you,” he said, and Sans blinked, but Gaster pressed on. “Did your brother tell you that he came to see me?”

“he… uh, yeah, he did,” Sans said. God it was so awful to hear his voice so tight with worry. 

“Did he tell you that I’m not upset?”

“...yeah. i figured he was just tryin’ ta cheer me up,” Sans said, but at least he seemed to be calming down.

Gaster didn’t know what to do. He walked over and pulled up a chair.

“May I sit?”

“y-yeah, of course.”

Gaster did so, but Sans was speaking again before he could even open his mouth.

“i’m sorry. about what happened- i know i went too far. i didn’t think before i did it, even if-” he broke off and gulped- “even if it wasn’t… what it was, it was still wrong. i’m sorry, sir, i just… i need this job. i’ll do anything, sir, but i-i  _ need _ this job.”

Gaster stared at him for a moment. He needed this job…? What job? He already had a job-

Realization struck like lightning and Gaster nearly gasped.

“God no, Sans, I’m not going to fire you!” he said immediately, watching the small skeleton’s eyes go wide. “I was- god, Sans, no, that- that’s absurd!”

Sans was sitting, and he stared with wide eyes.

“Sans- I’m not upset. What your brother told you is true,” he said, and it came out so much easier when Sans was sitting in front of him looking so miserable. “What happened was… well, it was inappropriate, but I’m not angry. My first thought was that it was a good opportunity for a joke, for God’s sake, I didn’t realize that you assumed I would…” Gaster trailed off. He was hardly ever flustered, but he was extremely flustered at that moment. “I’m sorry. I made a joke of a very serious situation and I gave you the wrong impression. I was never upset with you.”

Sans stared at him for a moment longer, as though in shock. Gaster sat back in his chair and waited.

“i… i mean…” Sans rubbed the back of his neck and looked away. He paused again before his shoulders started shaking.

“Sans-”

He was laughing. Gaster stopped and froze, but Sans kept laughing.

After a moment, he started crying.

Gaster had no idea what to do. Sans put his head down on his desk and continued to sob. Should he… say something? Do something? Dear god he wasn’t qualified for this.

“Are… are you okay, Sans?” 

“y-yeah, yeah i’m… i’m peachy,” he cried.

“You really do not sound okay.”

Sans looked up at him with tears running down his bones and oh god Sans was actually crying.

“i already thought out the rest of my life as a street vendor,” he bawled, but he was also sort of smiling, but mostly he was sobbing. “i was ready to work five jobs to support me ‘n pap, already knew how i was gonna say bye to al, oh my fucking god.”

Gaster was mortified. He stayed absolutely still and Sans continued to cry.

“i’m an idiot- holy shit, i’m such an idiot, oh my god-”

“You’re not an idiot,” Gaster said, and it seemed to draw Sans out of his little moment. Gaster cleared his throat. “Are you going to be alright?”

Sans stared at him before he slapped his hand to his face.

“oh my god. i literally just- i seriously just sat here and started bawling. i’m sorry, g, i just… i thought… i seriously thought you were going to give me the boot.”

“It’s quite alright, I understand.” Gaster sat back in his chair and let out a deep breath. Sans was still crying, but he used his lab coat to mop up the liquid and pretend like nothing had happened.

“i’m seriously sorry, though,” he said eventually. He looked down at his sandwich bag with sad eyes. “i went way too far.”

“No, no, it’s alright,” Gaster reassured, because it really was alright and dear god he didn’t know how to handle people getting so emotional. “Truthfully, I rather enjoyed it.”

Sans jerked his head up to look at Gaster. Gaster realized what he’d said a moment after it had slipped from between his teeth and wow it was hot in Sans’s office. 

“I- oh, that was extremely inappropriate to say, I’m so sorry-”

“n-no!” Sans protested as he raised his hands. “i did too- i mean it was yours so i thought about you-”

Gaster felt his soul bottom out and his blush grow to fever heights. Sans slapped his hands over his mouth.

“oh my fucking god i didn’t actually just say that,” he breathed from behind his fingers.

Gaster said nothing. Sans said nothing. Neither said a single word and the air was tight with… something. Gaster stared at his lap and processed that Sans had thought of him when he’d used his sex toy. Much to his dismay and embarrassment, it wasn’t an unpleasant thought.

“do you want to come over for dinner tonight?”

Gaster was taken completely offguard by the words and looked up at the other skeleton, still blue as his magic. Sans ran a hand along his skull and smiled sheepishly.

“pap told me to ask you. i, uh… i owe ya. for letting me keep my job.” Sans blushed and flashed his boss a quick glance before he looked away again. “plus, i dunno… might make things less awkward if pap’s there? he’s, uh… he’s pretty dominating when it comes to conversation.” Sans let out a nervous titter. “if you don’t want to that’s fine, i just-”

“That sounds lovely,” Gaster said, and Sans somehow managed to turn an even deeper shade of cerulean. 

“you sure? you don’t have to-”

“I’d very much enjoy that,” Gaster said, and he felt like a great burden had been lifted off of his shoulders. “Eating alone gets rather… well, lonely.”

Sans looked at him. He had a strange emotion in his eyes that Gaster couldn’t place.

“you uh… you know you can come to my place anytime you’d like, right?” Sans offered. “i think we’ve crossed that line by now… and, ‘sides, pap loves hearing about other people’s jobs and lives and stuff. he makes a mean pot of spaghetti.”

Gaster felt something very light and airy in his bones. He smiled.

“I’ll remember that.”


	4. Chapter 4

**Notes for the Chapter:**

> and here's the last chapter of this! thanks for reading!
> 
> (i also realize that i didn't caps lock papyrus's dialogue in chapter 2, i'll go back and fix that, but i did it here)

“DR. GASTER! I’M SO GLAD YOU COULD MAKE IT!”

Gaster smiled at the tall skeleton in front of him. Good god he hoped he was wearing the appropriate clothes for the occasion. He’d never actually… gone to anybody else’s home before. Papyrus stepped aside and beckoned him in. He was wearing an apron with the words “ultra chef 9000” on it, but beneath that he had on a simple tank top and jeans. Perhaps a shirt and tie wasn’t the best option.

“COME IN, MAKE YOURSELF AT HOME!” Papyrus chirped. “I’M MAKING DINNER NOW- SANS IS STILL GETTING READY, YOU CAN COME ACCOMPANY ME IN THE KITCHEN IF YOU’D LIKE.”

Gaster felt some of his nerves melt away. Papyrus grinned at him before he walked off. The doctor took a moment to look at the main living area of their apartment. 

It was clean, but in a way that showed it was lived in. A few dirty socks sat on the floor and on the backs of chairs, a few textbooks stacked haphazardly on the end table, an empty cup beside them. There was only a sofa and recliner, and the space wasn’t even as large as his own home, but it looked welcoming. Gaster looked at the pictures on the shelf as he walked behind Sans’s brother- all pictures of the two of them. There was even a picture of Sans on his first day at the labs. Gaster smiled.

“SANS SAID YOU WERE ALRIGHT WITH PASTA, BUT WE WERE ALL OUT OF RED SAUCE, I HOPE ALFREDO IS ACCEPTABLE AS WELL.”

Gaster nodded, still taking in the space around him. “That sounds perfect.”

“GOOD!” Papyrus said. The main living area led off to a hallway, and on the opposite side, the kitchen. Papyrus motioned for Gaster to sit at the table while he hurried over to the entrance of the hallway.

“SANS! OUR GUEST HAS ARRIVED! PUT SOME PANTS ON AND GET OUT HERE!”

The apartment was very much livelier than his home had ever been. Gaster sat back in his chair and watched the younger skeleton cook. He had the sauce cooking away in one pan while the noodles boiled in another. 

“It smells delicious,” Gaster said. Papyrus turned to face him with bright eyes.

“THANK YOU! ALFREDO IS ONE OF SANS’S FAVORITES, SO USUALLY I ONLY MAKE IT WHEN HE REQUESTS.”

“How long have you been cooking?” 

Papyrus paused to think. He idly stirred the alfredo sauce before narrowing his sockets.

“HMM… THAT’S A GOOD QUESTION! I SUPPOSE IT’S BEEN EVER SINCE I COULD.” Papyrus smiled wistfully down at his pasta. “AT FIRST IT WASN’T VERY… AH, EDIBLE, BUT! SANS WAS ALWAYS SO BUSY WORKING, MAKING HIM SOMETHING TO EAT WAS THE LEAST I COULD DO.”

Gaster nodded politely. He knew very little about Sans and Papyrus’s personal life, but he knew they had had financial troubles in the past. It was a situation that was foreign to him- he’d grown up having money in his family, the idea of not having enough to get by was… distressing.

“WHAT ABOUT YOU, SIR?”

Gaster looked up from the table top and blinked. 

“What?”

“COOKING! YOU LIVE ALONE, SO I HEAR, YOU MUST DO A FAIR SHARE OF IT YOURSELF,” Papyrus said. 

“Oh, yes,” Gaster said. He raised his hand to scratch at his bones. “I don’t cook very much. I’d rather buy things that are easy to prepare and keep in the freezer.”

Papyrus frowned at that. “THAT DOESN’T SOUND VERY APPETIZING… BUT I SUPPOSE THE ROYAL SCIENTIST HIMSELF DOESN’T HAVE A LOT OF TIME TO STAND AROUND AND STIR HIS SPAGHETTI!”

Gaster smiled and opened his mouth to say something along the lines of “no, I’m just lazy,” when he saw a familiar shape emerging from the hallway.

Sans, like his brother, also had on very casual clothes. A white shirt and blue jacket with basketball shorts- Gaster had certainly overdressed for the occasion. He felt silly in his black button-up and faded purple tie.

“damn g, you got yourself that cleaned up just for us?” Sans asked, and it made Gaster flush with magic.

“SANS!” Papyrus scolded immediately. “DR. GASTER IS OUR GUEST THIS EVENING! PERHAPS YOU SHOULD TRY DRESSING UP EVERY ONCE IN AWHILE.”

“hey paps, don’t try to  _ tie  _ me down.”

“SO, DR. GASTER, WE WILL BE DINING ALONE TONIGHT, BECAUSE I’VE JUST DISOWNED MY BROTHER.”

“aw come on pap-”

“IS SOMEBODY SPEAKING? I DON’T THINK ANYBODY IS SPEAKING.”

Gaster smiled.

  
  


The food was great. Sans and Papyrus bickered and joked, and Gaster’s fears of a tense atmosphere were put to rest. One of the brothers would direct the conversation back to Gaster, but the elder monster was enjoying them interacting as brothers. He’d never truly witnessed it before, and it was… heartwarming. 

Sans would flash him glances across the table. He looked both guilty and nervous, emotions that didn’t suit him at all. Gaster would quirk a brow and smile, which flustered Sans. Now  _ that _ was an appropriate way to get back at the other scientist, not pretending to be his angry boss.

Two hours passed by quite rapidly. Gaster’s soul began to flutter when Sans would flash him a sultry look over the table. It was just to rile him up and tease him… wasn’t it? Gaster would return the gestures. Was this a game? Was Sans  _ actually _ flirting? Gaster was just glad he was no longer crying. 

“OH MY, WOULD YOU LOOK AT THE TIME!” Papyrus exclaimed. Gaster did so. It was eight.

“Ah- should I be on my way?” the foreign skeleton asked, unsure of what was and was not socially acceptable to do in these situations.

“YES! AS LONG AS YOUR ‘WAY’ LEADS YOU TO SIT RIGHT BACK DOWN AT THIS TABLE,” Papyrus said with a wink. “I PROMISED MY FRIEND UNDYNE I WOULD STOP BY TONIGHT.”

“you didn’t tell me you were goin’ anywhere,” Sans said with a frown.

Papyrus grinned and elbowed his brother as he stood up. “OH, GEE, DIDN’T I? IT MUST HAVE SLIPPED MY MIND.”

Papyrus looked like he’d just pulled off the prank of the century. He patted Sans’s head before he strode to the door and pulled a jacket from the coat-rack. “I’LL BE BACK TOMORROW MORNING! HAVE FUN!”

The door shut behind him. Gaster stared at Sans. Sans stared at Gaster. A short moment passed before the short skeleton put his head on the table and groaned.

“i’m gonna kill him,” he deadpanned.

Gaster was preoccupied with his thoughts. Deliberately leaving he and Sans alone? It was as though Papyrus assumed they would- oh.

“listen g, if this is awkward you can leave, my bro is a fucking idiot sometimes with his happy-go-lucky romance plots to get people together, i’m not gonna ask you to stay.”

“Do you want me to?”

Sans lifted his head and blinked. Gaster once again felt his soul brighten. He was a little ashamed to be as happy as he was, given his age, but Sans was almost thirty himself. 

“i mean… yeah? I guess?” Sans rubbed the back of his neck and slouched in his chair. “you know he left us here cause he thinks were gonna…” Sans coughed awkwardly. “y’know.”

“What does he think we’re going to do?” Gaster asked with a shit-eating smile.

Sans blushed. “you know damn well what, you fuckin’ asshole.”

Gaster’s smile grew soft. “Sans- I don’t think that beating around the bush is going to do either of us any good. Perhaps we could try being honest?”

Sans was still flush, and he looked away, but he sighed in resignation. “no, no, you’re right. i’m no good at this emotional shit.” He peeked up at the other monster. “you go first.”

“However you react to this, I will not be upset, nor will it affect your position at the lab,” Gaster prefaced, keenly aware of Sans’s previous concerns. “But… if, hypothetically, you were not completely disgusted by the idea of having a…  _ relationship _ … of some kind or another… I would not be opposed to that idea,” Gaster said, as straightforward and factual as he could, while still avoiding any sort of statement that could make Sans feel trapped. “But, if you  _ were _ to have qualms about such a thing, I would not be offended, nor would I think any less of you.”

Sans sat back and processed that. He looked about as uncomfortable as Gaster felt.

“honestly, g, i’m… not at all against it,” Sans began as he folded his hands on the tabletop and kept his eyes down. “i like you, you’re a great guy. you’re just… you’re way up here, y’know?” Sans met the other monster’s eyes. “like… here I am-” he held his hand an inch or two about the surface of the table, “- and here’s you-” he put his hand up as high as it would go. “you’re the royal scientist, you’re clean and all formal and shit and i’m… not that. and i don’t think i can change it, either.”

“If you started acting like I do, I would begin to like you progressively less,” Gaster said with a small laugh. “I quite enjoy all of those things about you. I wouldn’t want you to change.”

Sans was quiet. He didn’t meet Gaster’s eyes, and he looked conflicted. Gaster waited patiently for a few moments before Sans exhaled.

“you bein my boss won’t affect anything?” he asked quietly. “like… if we start gettin to know each other better and you find out you hate me, you’re not gonna fire me?”

“I swear on my life,” Gaster promised. “I was thinking about giving you a promotion, before all of this happened. The Assistant Royal Scientist.” Gaster laughed at the look of awe on Sans’s face. “If you were ever to quit your job at the lab, it’s certainly something to put on a resume.”

“oh my god,” Sans said. His face broke and he started laughing. “so if i date you you’re gonna give me a raise?”

“That will happen either way,” The elder skeleton said with a wave of his hand. “You’ve been working extraordinarily hard. I’m afraid the only perks that come with me are the fleshlight and copious amounts of instant noodles.”

Sans snorted before he started laughing again, in earnest. The atmosphere was finally back to normal. Gaster felt a huge weight lift from his shoulders as Sans wiped a stray tear from his socket.

“fuck, you know i can’t say no to ramen and sex toys.” Sans leaned forward onto the table, head propped up by his palm. “i say we give it a go. if it doesn’t work, it doesn’t work.”

“That seems fair. I don’t have much experience, Dr. Fontaine, is the next step in the courting ritual to have brutal intercourse on the sofa?”

Sans barked out a curse and stood up, shoulders shaking with his bouts of laughter. He walked around the table and offered Gaster his hand. He looked… happy.

“well, y’know, usually it’s kissing, but we don’t really have lips.”

Gaster took his hand and stood. He was much taller than Sans, and in his rush of happy adrenaline he grabbed Sans under his arms and hoisted him up onto the table.

“w-woah there, g,” he said, but he was still giddy. Gaster was much the same.

“It isn’t my fault you’re incredibly short,” the elder monster said as he stood close, close to eye level with his colleague. He got close and held Sans’s hand. 

“didja bring the fleshlight?” Sans asked.

His temporary courage told him to put his head beside the small skeleton’s, and he listened to it.

“It’s only fair that I get to take lead tonight.”

Sans pulled back, flush. “that doesn’t sound like somebody who doesn’t have much experience.”

“I meant in romance,” Gaster clarified, but he pulled away for a moment. “I’ve had my fair share of sexual encounters.”

“oh. i, uhm… oh.” Sans leaned back with his face full-blue.

“Is something wrong?”

Sans was quick to shake his head. “nah, i just assumed… you didn’t do this kind of thing?”

“I’m a scientist, not a nun.”

Sans laughed. “heh, yeah…”

“Have you ever done this before?” Gaster asked, trailing a hand along Sans’s ribs as sensually as he could. Sans didn’t seem to expect it. His body jerked at the touch.

“n-no…” he confessed. “i’m more of a… solo kinda guy.”

“Do you  _ want _ to do this?” Gaster pulled his hand away in worry that he’d crossed a line, but Sans grabbed it and pulled it back.

“fuck yeah,” he murmured in a low and sexy voice that Gaster had never heard him use.

That was all it took. Gaster leaned forward and pressed their teeth together, and Sans tilted his head back to allow the contact. Gaster’s hands worked across Sans’s ribs, under his shirt, while Sans held the taller skeleton’s shoulders and did his best to return the gestures.

“fuck, g,” Sans gasped as the monster’s spine was stroked. He fell forward into Gaster’s touch as his breath hitched. 

“You already fucked me, Sans,” he said. Sans huffed in amusement before Gaster pawed at his cock through his shorts.

“ngh-” Sans cut himself off by biting Gaster’s shoulder, which only made his ministrations firmer. Sans didn’t have a long cock, but it was certainly thick. Gaster rubbed it with one hand while his other was busy working Sans’s spine, which was arched into the touch. Sans’s femurs twitched and clacked on the tabletop.

Gaster felt his own pelvis grow hot at the little noises that escaped Sans’s mouth. They were intoxicating- he would have never expected Sans to be vocal in bed. He tugged down the waistband of his charge’s shorts and allowed his cock to spring up and free of the fabric. Precum was already dripping down its length, and as Gaster pressed roughly against Sans’s lower spine it twitched. 

“f-fuck, g,” Sans gasped. “don’t just- pull it out and leave it hangin-”

Gaster laughed as he wrapped his hand around Sans’s length, smearing the thick fluid up its length and back down. Sans moaned.

“It seems dirty talking isn’t one of your areas of expertise,” Gaster said as he continued his movements, up and down Sans’s length, swirling his thumb over the head. Sans seemed almost lost in the primal feeling.

“you’re such… an ass,” Sans said. “i’m- i’m great at sex talk.”

“The fact that you just called it ‘sex talk’ proves otherwise.”

Sans removed his hand from Gaster’s shoulder and wrapped it around Gaster’s own dick. The elder skeleton sucked in a breath from the unexpected contact.

“fuck me on the table, boss,” Sans growled as he began to unbutton Gaster’s shirt.

The shirt was off in seconds and Gaster’s pants were around his ankles. Sans tugged his shorts off and flipped over so his ass was in the air. Gaster hardly had the patience to stretch Sans out first, but he continued to jerk Sans off while he fingered his ass.

“oh my god,” Sans panted as his femurs clamped together as much as the table allowed. “fuck- come on- more-”

“Have you ever been anally penetrated?”

“and you said i’m bad at dirty talk-”

“There’s nothing arousing about unsafe sex,” Gaster said like the responsible person he was.

“god- no, I have toys, mr. safe sane and consensual. you got a foot long schlong or something?”

Gaster added another finger, and Sans moaned.

“It is above average,” Gaster said. He rubbed just behind the head of Sans’s cock and the skeleton thrust himself backwards onto Gaster’s hand.

“god damnit-  _ fuck me already _ .”

Gaster took his hand off of Sans’s length to stroke himself a few times. He was already hard.

“Where’s your lube?”

“oh my god just spit on it or something-”

“It will feel better with proper lubrication.”

“gaster i swear to god-”

“Who had the greater amount of experience here?” Gaster asked.

Sans kicked him away and got up with a few mumbled curses. He all but ran back down the hallway, and appeared again in seconds with the bottle in his hands.

“there- there’s the lube- now slather it on your fucking- oh my god that is a big dick,” Sans said in quiet awe.

“I told you,” Gaster said as he hoisted Sans back up on the table and took the bottle from his hands. “Tell me if it’s too much.”

Sans didn’t say anything. He seemed to brace himself against the table, though, which made the bigger monster laugh.

“Relax- it’ll go in easier.”

“this is nothing like first time sex in a porno,” Sans commented in a nervous pitch as Gaster applied the lubricant.

“Those are highly unrealistic, not to mention aggressively unsafe.” Gaster put his fingers back inside of the smaller skeleton and gently played with him until the tension melted out of his bones.

In one fluid movement, Gaster slid half of his cock into Sans.

“ah- fuck- fuck-” Sans gasped. “fuck you’re big- jesus christ-”

“Too much?” Gaster said through his teeth. Sans was tight, near painfully so.

“no i’m good- just- fuck. fuck. give me a second.” Sans breathed. He hissed as he arched his back and turned to look at Gaster. His face was flushed blue and he was sweating- he looked absolutely incredible.

“heh… oh god… i can’t believe we’re actually doing this. your dick is in my literal asshole.”

“Do you want to stop?”

“god no,” he said. “take me to pound town, boss.”

Gaster pulled out, slowly, before easing himself back in. Sans groaned and gritted his teeth, head falling back to the table. 

Gaster built a rhythm, slow and steady at first. Sans felt amazing around his length- it wasn’t long before he was burying himself hilt-deep inside of him.

“You’re… quite good,” Gaster said, feeling a little breathless himself as the pleasure pooled at his pelvis, warming his bones and making them feel soft.

“harder, g, please,” Sans begged. 

If Gaster hadn’t been turned on before, he certainly was now. He pulled out almost all the way before jamming back in. Sans let out a deep, guttural moan upon being filled so fully.

Gaster fucked him. Sans squirmed on the tabletop, moaning and grinding back against Gaster’s movements, breathless, panting, pleading for more. His jacket was bunched up around the shoulders. Gaster’s ribs were bare and he felt lewd, screwing Sans on the table like this, but that just made him thrust faster and harder, which made Sans cry out in primal pleasure.

“g- fuck- gaster- i-i’m fuckin- i’m close-”

“Cum for me,” Gaster said, taken aback by the desperation in his own voice. He was close as well.

“oh my god-” Sans’s voice cut off as Gaster hilted inside of him, thrusts growing more erratic the closer he got.

“Cum for me, Sans,” he breathed. 

“gaster- i’m- i’m gonna-”

He didn’t finish the thought. Gaster felt his ass throb as he came, and he saw the cum hit the floor and the table as Sans pumped his load with loud, unchecked moans. 

Gaster didn’t last much longer. He felt the heat build and the ungodly wonderful feeling of orgasm overwhelm him all at once. He hunched over the table, over Sans’s entire body as he spent himself inside, thrusting shallowly as the spurts of cum ended and he was left breathless on the table.

Neither said anything for a moment. Gaster leaned forward and did what felt right- he kissed the side of Sans’s skull before he pulled out, a gross mixture of lube and his own cum spilling in the wake of his cock. Sans stirred and brought himself up with his shaking arms to turn back and look at Gaster.

“h… holy fuck,” he said, looking down at the mess they’d made. “that was… that was fucking amazing.”

“Yes,” was all Gaster could think to say. He disappeared into the kitchen for a moment and returned with paper towels.

“are you… cleaning it up?”

Gaster was already on his knees, wiping up the puddle of fluids as best he could. “I don’t think your brother would appreciate it if he came home to… this.”

“hah, you’re right, but i coulda… coulda done that,” Sans said, still shaky and a little out of breath.

“You seem quite spent,” Gaster said with a little smile. He cleaned the mess on the tabletop before he went back and threw the used tissues away.

“yeah… i’m just a lil tired,” Sans said with a grin. 

He didn’t seem prepared for Gaster to scoop him up in his arms, but he didn’t protest. 

“woah- where’re we goin?” Sans asked in amusement.

“Your bedroom. I don’t think Papyrus would appreciate us half naked on the couch, either.”

Sans chuckled before he rested his head against Gaster’s chest. He pointed out his bedroom and, as expected, it was quite a disaster. Gaster ignored it and plopped Sans down on the mattress before joining him.

“so… what’d ya think?” he asked, blearily, clearly trying his hardest to stay awake.

“It was quite enjoyable,” Gaster said. He threw the blanket over them both and Sans laughed. Gaster laid back and before he could continue, Sans flipped over and wrapped his arms around Gaster’s chest.

“damn straight it was,” Sans said with another laugh. “if we’re boyfriends we can do that all the time, right?”

“That is the idea, yes.”

“will you be my boyfriend?” Sans asked. He looked half asleep already, curled up around the bigger monster, breathing slowly.

“Yes, Sans,” Gaster said with a smile. He looped an arm around the small skeleton’s frame. “Go to sleep, Sans.”

“yeah.. you got it, boss,” Sans said. “lets… lets… take a lil… nap…”

He was asleep before he finished the thought. Gaster smiled and leaned over to plant a little kiss on his forehead.

This could work. This could definitely work.

  
  


They were both woken the next morning by the front door slamming shut.

“I’M HOME! DID YOU TWO HAVE ROMANTIC, HEATED INTERCOURSE?”

Sans groaned.


End file.
